Missingno does exist but its not in the pokedex and it never will in the National pokedex. YOu ave to use the Action Replay's Walk through wall cheat and you have to be escorting a person through Stark Mountain, Iron Island, or any place where you can walk anywhere when a pokemon can attack. Walk to the Mystery Zone with your partner left behind. When you fight 2 pokemon at a time, there is a good chance that the pokemon on the right is a missingo.

DO NOT CATCH IT!!!! MISSINGO'S EFFECT IS UNKNOWN IN POKEMON DIAMOND AND PEARL! I STRONGLY RECOMMEND THAT YOU DO NOT CATCH IT!!!!!

Do you know how hard it is to type on a PSP?

[CENTER][IMG]http://www.wizards.com/magic/images/whatcolor_isred.jpg[/IMG][URL=http://www.wizards.com/magic/playmagic/whatcolorareyou.asp][B]Take the Magic: The Gathering 'What Color Are You?' Quiz.[/B][/URL][/CENTER]

i also know how to get a missingno(as everyone is saying and as i am DO NOT SAVE OR CATCH IT!!!) first use the instant egg & the fast egg hatch with 1 or no pokemon in the daycare center and talk to the guy who gives you pokemon eggs ang he will give you a missingno egg. walk 2 steps, it should hatch into a missingno, or as the game says, would you like to nickname the newly hatched ------?. do not save. also you cannot send misingno into battle, get him out of team or release it you must cut the power without saving.hope that helps